[BUILD] Add cxx feature detections (open-telemetry#3203)

Author: owent

CMakeLists.txt

@@ -645,6 +645,37 @@ if(BUILD_TESTING)
   endif()
   message(STATUS "GTEST_INCLUDE_DIRS   = ${GTEST_INCLUDE_DIRS}")
   message(STATUS "GTEST_BOTH_LIBRARIES = ${GTEST_BOTH_LIBRARIES}")
+
+  # Try to find gmock
+  if(NOT GMOCK_LIB AND TARGET GTest::gmock)
+    set(GMOCK_LIB GTest::gmock)
+  elseif(MSVC)
+    # Explicitly specify that we consume GTest from shared library. The rest of
+    # code logic below determines whether we link Release or Debug flavor of the
+    # library. These flavors have different prefix on Windows, gmock and gmockd
+    # respectively.
+    add_definitions(-DGTEST_LINKED_AS_SHARED_LIBRARY=1)
+    if(GMOCK_LIB)
+      # unset GMOCK_LIB to force find_library to redo the lookup, as the cached
+      # entry could cause linking to incorrect flavor of gmock and leading to
+      # runtime error.
+      unset(GMOCK_LIB CACHE)
+    endif()
+  endif()
+  if(NOT GMOCK_LIB)
+    if(MSVC AND CMAKE_BUILD_TYPE STREQUAL "Debug")
+      find_library(GMOCK_LIB gmockd PATH_SUFFIXES lib)
+    else()
+      find_library(GMOCK_LIB gmock PATH_SUFFIXES lib)
+    endif()
+    # Reset GMOCK_LIB if it was not found, or some target may link
+    # GMOCK_LIB-NOTFOUND
+    if(NOT GMOCK_LIB)
+      unset(GMOCK_LIB)
+      unset(GMOCK_LIB CACHE)
+    endif()
+  endif()
+
   enable_testing()
   if(WITH_BENCHMARK)
     # Benchmark respects the CMAKE_PREFIX_PATH

api/include/opentelemetry/detail/preprocessor.h

@@ -11,3 +11,15 @@
 
 #define OPENTELEMETRY_CONCAT(A, B) OPENTELEMETRY_CONCAT_(A, B)
 #define OPENTELEMETRY_CONCAT_(A, B) A##B
+
+// Import the C++20 feature-test macros
+#ifdef __has_include
+#  if __has_include(<version>)
+#    include <version>
+#  endif
+#elif defined(_MSC_VER) && ((defined(__cplusplus) && __cplusplus >= 202002L) || \
+                            (defined(_MSVC_LANG) && _MSVC_LANG >= 202002L))
+#  if _MSC_VER >= 1922
+#    include <version>
+#  endif
+#endif

exporters/elasticsearch/src/es_log_recordable.cc

@@ -1,11 +1,17 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#include <opentelemetry/version.h>
+
 #include <chrono>
 #include <ctime>
 #include <nlohmann/json.hpp>
 #include <string>
 
+#if defined(__cpp_lib_format)
+#  include <format>
+#endif
+
 #include "opentelemetry/exporters/elasticsearch/es_log_recordable.h"
 #include "opentelemetry/logs/severity.h"
 #include "opentelemetry/nostd/variant.h"
@@ -71,7 +77,8 @@ void ElasticSearchRecordable::SetTimestamp(
 
   // If built with with at least cpp 20 then use std::format
   // Otherwise use the old style to format the timestamp in UTC
-#if __cplusplus >= 202002L
+  // @see https://en.cppreference.com/w/cpp/feature_test#cpp_lib_format
+#if defined(__cpp_lib_format) && __cpp_lib_format >= 201907
   const std::string dateStr = std::format("{:%FT%T%Ez}", timePoint);
 #else
   std::time_t time = std::chrono::system_clock::to_time_t(timePoint);

exporters/otlp/CMakeLists.txt

@@ -313,29 +313,6 @@ if(BUILD_TESTING)
     TEST_PREFIX exporter.otlp.
     TEST_LIST otlp_metrics_serialization_test)
 
-  if(NOT GMOCK_LIB AND TARGET GTest::gmock)
-    set(GMOCK_LIB GTest::gmock)
-  elseif(MSVC)
-    # Explicitly specify that we consume GTest from shared library. The rest of
-    # code logic below determines whether we link Release or Debug flavor of the
-    # library. These flavors have different prefix on Windows, gmock and gmockd
-    # respectively.
-    add_definitions(-DGTEST_LINKED_AS_SHARED_LIBRARY=1)
-    if(GMOCK_LIB)
-      # unset GMOCK_LIB to force find_library to redo the lookup, as the cached
-      # entry could cause linking to incorrect flavor of gmock and leading to
-      # runtime error.
-      unset(GMOCK_LIB CACHE)
-    endif()
-  endif()
-  if(NOT GMOCK_LIB)
-    if(MSVC AND CMAKE_BUILD_TYPE STREQUAL "Debug")
-      find_library(GMOCK_LIB gmockd PATH_SUFFIXES lib)
-    else()
-      find_library(GMOCK_LIB gmock PATH_SUFFIXES lib)
-    endif()
-  endif()
-
   if(WITH_OTLP_GRPC)
     add_executable(otlp_grpc_exporter_test test/otlp_grpc_exporter_test.cc)
     target_link_libraries(

exporters/zipkin/CMakeLists.txt

@@ -49,17 +49,6 @@ if(BUILD_TESTING)
     TEST_PREFIX exporter.
     TEST_LIST zipkin_recordable_test)
 
-  if(MSVC)
-    if(GMOCK_LIB)
-      unset(GMOCK_LIB CACHE)
-    endif()
-  endif()
-  if(MSVC AND CMAKE_BUILD_TYPE STREQUAL "Debug")
-    find_library(GMOCK_LIB gmockd PATH_SUFFIXES lib)
-  else()
-    find_library(GMOCK_LIB gmock PATH_SUFFIXES lib)
-  endif()
-
   add_executable(zipkin_exporter_test test/zipkin_exporter_test.cc)
 
   target_link_libraries(

test_common/src/http/client/nosend/CMakeLists.txt

@@ -8,25 +8,6 @@ if(${BUILD_TESTING})
   set_target_properties(opentelemetry_http_client_nosend
                         PROPERTIES EXPORT_NAME opentelemetry_http_client_nosend)
 
-  if(MSVC)
-    # Explicitly specify that we consume GTest from shared library. The rest of
-    # code logic below determines whether we link Release or Debug flavor of the
-    # library. These flavors have different prefix on Windows, gmock and gmockd
-    # respectively.
-    add_definitions(-DGTEST_LINKED_AS_SHARED_LIBRARY=1)
-    if(GMOCK_LIB)
-      # unset GMOCK_LIB to force find_library to redo the lookup, as the cached
-      # entry could cause linking to incorrect flavor of gmock and leading to
-      # runtime error.
-      unset(GMOCK_LIB CACHE)
-    endif()
-  endif()
-  if(MSVC AND CMAKE_BUILD_TYPE STREQUAL "Debug")
-    find_library(GMOCK_LIB gmockd PATH_SUFFIXES lib)
-  else()
-    find_library(GMOCK_LIB gmock PATH_SUFFIXES lib)
-  endif()
-
   target_link_libraries(
     opentelemetry_http_client_nosend opentelemetry_ext
     opentelemetry_test_common ${GMOCK_LIB} ${GTEST_BOTH_LIBRARIES})